1. Field of the Invention
Magnetic recording devices include a magnetic recording layer in which individual bits are recorded as magnetized spots having at least two detectably different magnetic orientations. It has been discovered that a particularly valuable type of recording layer can be made from a thin coating of cobalt metal deposited on a non-magnetic substrate. Experience shows that not all non-magnetic substrates are suitable for carrying the cobalt layer. On some substrates, the adherence of the cobalt film is not sufficient to resist the mechanical stresses which ordinary use places on it, resulting in its flaking and removal from the substrate during use. In other situations, the cobalt will not form a layer of uniform coercivity, resulting in undesirable variations in the magnetic recording qualities of the cobalt layer.
2. Description of the Prior Art
U.S. Pat. No. 3,738,818 (Stone et al), having common ownership with this application, and U.S. Pat. No. 3,702,239 (Nagy et al) both teach the preparation of a substrate for a cobalt recording film comprising a nickel inner layer and a gold outer layer on which the cobalt layer is placed. In both cases, the nickel and gold layers are deposited from a chemical solution. U.S. Pat. No. 3,433,721 (Wolff) discloses the use of a sputtered gold substrate beneath a permalloy magnetic film. U.S. Pat. No. 3,348,931 (Reekstin) discloses depositing a gold film on a copper substrate, with a layer of Fe-Ni-Cu plating which serves as the magnetic recording layer. U.S. Pat. No. 3,297,418 (Firestone et al) discloses a deposited gold film on which is deposited a magnetic recording layer comprising nickel, cobalt and iron. U.S. Pat. Nos. 3,180,715 and 3,549,418 and 3,607,149 all disclose cobalt magnetic recording layers having a non-magnetic substrate layer immediately beneath.